PROJECT SUMMARY This proposal will develop the High-Throughput Spheroid Screening Platform (HTSSP) to create an entirely new tool to study cell-cell interactions and microenvironmental stresses that occur in tissues and tumors. Such interactions are critical in the pharmaceutical response of cells within tissues, but current methods do not allow high throughput screening (HTS) of cellular responses in a tissue-like microenvironment. The HTSSP is being developed to enable the use of the powerful multicellular spheroid 3D tissue/tumor model system, which has many potential applications in 3D drug screening, in true high-throughput screening (HTS) applications. To create the HTSSP, we are addressing critical limitations in large particle analysis via flow cytometry (Aim 1), continuous sample handling of large particles such as spheroids (Aim 2), improving analytical methods to obtain spatial/structural information from spheroids in analysis (Aim 3), and demonstrating key applications of the HTSSP in real world assays (Aim 4). To improve flow cytometry analysis, we will optimize our current high throughput parallel flow cytometer (the 10xFC) by modifying the flow cells and the optics for ideal use with particles between 100 and 1000 microns in diameter. This flow cytometer will be integrated with an innovative suspension culture and sampling fluidic system to create the hardware of the HTSSP. These fluidics will maintain multiple samples of spheroids in stirred suspension chambers during incubation or exposure to drugs, then use the same chambers for sampling and resampling for analysis by our flow cytometer. The final synergistic technical achievement will be the development of improved data acquisition systems that enable the rapid extraction of 3D location information from probes within a spheroid. When combined with the hardware, this will synergistically complete the HTSSP, which will be used for key high-throughput pharmaceutical screening applications, including: apoptosis/necrosis induction, fraction of each cell type in a co-culture, fluorescent drug uptake. Taken as a whole, the HTSSP will represent a significant technological advance in pharmaceutical screening as it will provide the first truly high throughput approach to the study of pharmaceutical interactions in a 3D tissue model.